The present invention relates to chromium oxide or chromium oxynitride coated filament wear guides and to the method of their manufacture.
As is well-known to workers in the field, in the handling of threads, yarns and the like, the guide structures over which the threads, etc. pass must be characterized by both excellent wear resistance and controlled friction as between the running thread and the guide surface. The problem has been somewhat magnified in recent years by the development and growing use of synthetic threads which are even more abrasive than naturally occurring fibers. For efficient production without undue down time to replace the guide members (along with the replacement cost thereof) it is highly desirable that such guides serve for very extended periods without causing filament damage. To provide a method of readily and easily producing such desirable new guides is one of the principal purposes of this invention. As is set out below in some detail the oxidized or nitrided and oxidized structures produced as herein taught are very well suited for textile wear guide purposes.
We recognize that, generally speaking, the use of a chromic oxide surface on a thread guide device is old in that art. See U.S. Pat. No. 3,080,135 of R. P. Steijn. Such patent discloses the making of textile wear guides having a chromic oxide operating surface by the following methods:
A. from solid chromic oxide pieces--ceramics--followed by grinding to the desired smoothness; and PA1 B. flame spraying of chromic oxide onto a substrate, then followed by grinding, etc., to the desired smoothness.
In practice we find that such prior art devices suffer various shortcomings which are readily overcome by the use of the present invention. The solid ceramics not only are relatively brittle, with the attendant handling and installation problems in commercial use, but also are generally made with a high friction surface which necessitates complex secondary finishing operations to provide controlled friction at the surface. Similarly, the ceramic coated metals, produced by flame spraying do not inherently have usable low friction surfaces as fabricated. Both of these materials are rather rough, have undesirable snagging characteristics, and cause yarn damage unless extensively finished in a secondary operation.
It also should be noted that many textile wear guides are very small structures. As is alluded to in the Steijn patent, the chromic oxide flame spraying technique is mostly limited in application to parts having relatively simple geometry because of the line-of-sight nature of the process.
U.S. Pat. Nos. 3,526,486 and 3,567,599 disclose the oxidizing of very thin chromium plating to improve the corrosion resistance of the structures. Similarly, U.S. Pat. No. 3,480,483 shows the oxidation of very thin chromium coatings applied to the cutting edges of razor blades. U.S. Pat. No. 3,743,551 is directed to razor blades also having exceptionally thin coatings of chromium oxide and nitride thereon. All such coatings which have a maximum thickness of a few hundred Angstrom units, do not have the outstanding abrasive filament wear resistance as produced in the devices of our invention.
Another prior art patent is that of Rudness, U.S. Pat. No. 3,787,229 "Low Friction, Wear Resistant Material". Here spheres or spheroids of various ceramic materials are partially embedded in a matrix or binder layer. Mentioned as binders are various resins, rubber, ceramic, glass and metal which are capable of adhering to the substrate and of retaining the embedded rounded particles thereon. Such patent shows that the resulting surface consists of at least two substances--the hard, discrete particles embedded in a softer matrix binder.
In the present invention, on the other hand, a chromium layer deposited on the filament wear guide shaped substrate is oxidized or oxynitrided by reaction with an oxidizing or oxy-nitriding reactant to form a surface which is in conformity with the layer. If such layer is smooth and uninterrupted the chromium oxide or oxy-nitride replicates on this. If the chromium layer has a so-called "matte" finish, i.e., somewhat wavy, so also with the reaction layer reacted thereon. And if the chromium has a crack mosaic, as is oftentimes the case, the reaction product conforms to this with the added proviso that the reaction layer or zone is quite continuous.
Furthermore, in distinction to such prior art teachings, we have developed a method of forming either chromium oxide or chromium oxynitrided coated thread guides, or the like, which are not brittle, have excellent handling characteristics, are formed directly upon oxidizing or nitriding plus oxidizing without the necessity of a secondary surfacing operation, and are useful in making thread guides of practically any size.
The chromium oxide or oxy-nitride surfaces resulting herefrom also offer numerous advantages which will be set forth as this description proceeds.
In the present invention, a chromium deposit on a substrate member in the form of a textile wear guide is oxidized or nitrided plus oxidized.
Accordingly, a principal object of our invention is to provide devices characterized by excellent filament wear abrasion resistance and controllable friction to filaments passing thereover by the practice of the present process.
Another object of our invention is to provide a novel method of producing filament wear guides having an oxidized or nitrided plus oxidized chromium surface zone thereon.
These and other objects, features and advantages of our invention will become apparent to those skilled in this art from the following detailed disclosure thereof and the accompanying drawing, FIG. 1, which illustrates one representative embodiment of the present devices.
In the present specification reference is made to "thermally formed" oxide or oxy-nitride layers on a chromium surface. By this is meant that such layers are formed by reaction with oxygen or nitrogen and oxygen at elevated temperatures.